Flexible display substrate and method for manufacturing the same

ABSTRACT

Disclosed is a flexible display substrate and a method for manufacturing the same which can avoid break and peeling of film layers disposed on a flexible base and further reduce degree of a warpage occurred in the flexible base when separating the support substrate from the flexible base located above the support substrate. The flexible display substrate comprises the flexible base, a first buffer layer and a second buffer layer disposed on an upper surface and a lower surface of the flexible base, respectively, and a plurality of display modules disposed on the first buffer layer, each display module includes at least one thin film transistor and at least one electrode corresponding to the thin film transistor.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention generally relate to a displayapparatus, in particularly to a flexible display substrate for a displayapparatus and a method for manufacturing the same.

2. Description of the Related Art

Flexible display technology has been rapidly developed in recent years,which lead to great progresses in a flexible display from a screen sizeto a display quality. Both a Cathode Ray Tube (CRT) and a Liquid CrystalDisplay (LCD) belong to a rigid display. Compared with the rigiddisplay, a flexible display has many advantages such as impactresistance, shock resistance, light weight, small size, portability andthe like.

A method for manufacturing the flexible display generally comprisesforming a flexible base on a support substrate, and then further formingrespective film layers constituting a display module on the flexiblebase. A method for manufacturing the flexible base is often divided intotwo types, one is to affix films on the support substrate such as aglass substrate, the other is to coat the films on the supportsubstrate.

However, since a surface roughness of the flexible base is often greaterthan that of the glass substrate, in a case of bending, a break orpeeling of the film layers disposed on the flexible base is easilyoccurred due to an uneven surface of the flexible base and stressfactor.

In addition, during manufacturing the flexible display, the flexiblebase and the respective film layers will expands at a high temperature,and will shrink during the temperature is reduced from the hightemperature to a room temperature. In this process, due to difference inexpansion coefficients of the flexible base and the respective filmlayers, the flexible base will generally generate a greater deformation.Here, “a greater deformation” should be understood to be resulted from agreater stress. Therefore, when separating the flexible base from thesupport substrate, a warpage phenomenon is often occurred.

SUMMARY OF THE INVENTION

Embodiments of the present invention provide a flexible displaysubstrate and a method for manufacturing the same, which may avoid breakand peeling of film layers disposed on a flexible base and furtherreduce degree of a warpage generated by the flexible base whenseparating the support substrate and the flexible base located above thesupport substrate.

According to an aspect of embodiments of the present invention, there isprovided a flexible display substrate comprising a flexible base, afirst buffer layer and a second buffer layer disposed on an uppersurface and a lower surface of the flexible base respectively, and aplurality of display modules disposed on the first buffer layer, eachdisplay module including at least one thin film transistor and at leastone electrode corresponding to the thin film transistor.

In the flexible display substrate as described above, the first bufferlayer and the second buffer layer are made of the same material and havethe same thickness.

In the flexible display substrate as described above, any one of thefirst buffer layer and the second buffer layer includes at least onebuffer film layer, and all the buffer film layers of the first bufferlayer and all the buffer film layers of the second buffer layer aresymmetrically disposed with respect to the flexible base, respectively.

In the flexible display substrate as described above, a thickness ofeach of the first buffer layer and the second buffer layer is between1000 and 5000 Å.

In the flexible display substrate as described above, a plurality ofauxiliary film layers are disposed on one side of the second bufferlayer which is away from the flexible base, each of the auxiliary filmlayers being made of the same material and having the same thickness aseach pattern layer of the thin film transistor.

In the flexible display substrate as described above, an arranging orderof the plurality of auxiliary film layers is same as that of therespective pattern layers of the thin film transistor with respect tothe flexible base.

In the flexible display substrate as described above, a plurality ofauxiliary thin film transistors are disposed on one side of the secondbuffer layer which is away from the flexible base, the auxiliary thinfilm transistors corresponding to the thin film transistors one by one,respectively.

In the flexible display substrate as described above, the at least oneelectrode includes a cathode and an anode electrically connected with adrain electrode of the thin film transistor, and each of the displaymodules further includes a packaging layer and an organic materialfunctional layer disposed between the cathode and the anode.

In the flexible display substrate as described above, the at least oneelectrode include a pixel electrode electrically connected with a drainelectrode of the thin film transistor.

According another aspect of the embodiments of the present invention,there is provided a method for manufacturing a flexible displaysubstrate comprising steps of: forming a second buffer layer on asupport substrate; disposing a flexible base on the second buffer layer;forming a first buffer layer on the flexible base; forming a pluralityof display modules on the first buffer layer, each of the plurality ofdisplay modules including at least one thin film transistor and at leastone electrode corresponding to the thin film transistor, and separatingthe support substrate from the second buffer layer.

In the method as described above, the first buffer layer and the secondbuffer layer are formed under the same process condition.

In the method as described above, any one of the first buffer layer andthe second buffer layer includes at least one buffer film layer, and allthe buffer film layers of the first buffer layer and the second bufferlayer are symmetrically disposed with respect to the flexible base,respectively.

The method as described above further comprises steps of: forming aplurality of auxiliary film layers between the second buffer layer andthe support substrate, the auxiliary film layers being made of the samematerials and having the same thicknesses as the pattern layers of thethin film transistor, respectively, and separating the support substratefrom one of the plurality of auxiliary film layers in contact with thesupport substrate in the step of separating the support substrate fromthe second buffer layer.

In the method as described above, an arranging order of the plurality ofauxiliary film layers is same as that of the respective pattern layer ofthe thin film transistor with respect to the flexible base.

The method as described above further comprises steps of: forming aplurality of auxiliary thin film transistors between the second bufferlayer and the support substrate, the auxiliary thin film transistorscorresponding to the thin film transistors one by one, respectively; andseparating the support substrate from one of the plurality of auxiliarythin film transistors which is in contact with the support substrate inthe step of separating the support substrate from the second bufferlayer.

In the flexible display substrate and the method for manufacturing thesame according to various embodiments of the present invention asdescribed above, it is possible to cause strong adhesion forces to begenerated between the first buffer layer and the flexible base as wellas between the first buffer layer and the film layer located above thefirst buffer layer by forming the first buffer layer on the uppersurface of the flexible base, thereby not only solving a problem thatthe surface of the flexible base is rough, but also avoiding the breakand the peeling of the film layer on the flexible base.

Further, it is possible to counteract a part of stresses applied to theflexible base by the film layer located above the flexible base byforming the second buffer layer on the lower surface of the flexiblebase, so that the degree of the warpage occurred in the flexible basewhen separating the support substrate from the flexible base is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more apparently describe the embodiments of the presentinvention or the technical solution of the prior art, Figs. necessaryfor the embodiments or the prior art will be described simplyhereinafter. Obviously, the described embodiments are merely part of theembodiments of the present invention, other embodiments may be acquiredby the person skilled in the art based on the embodiments of the presentinvention without any inventive effort. The above and other features ofthe present invention will become more apparent by describing in detailexemplary embodiments thereof with reference to the accompanyingdrawings, in which:

FIG. 1 is a schematic view showing a bonding manner of a flexible baseand a support substrate in a process of manufacturing a flexible displaysubstrate according to exemplary embodiments of the present invention;

FIG. 2 is a schematic view showing a state in a process of manufacturinga flexible display substrate according to a first exemplary embodimentof the present invention;

FIG. 3 is a schematic view showing a state in a process of manufacturinga flexible display substrate according to a second exemplary embodimentof the present invention;

FIG. 4 is a schematic view showing a state in a process of manufacturinga flexible display substrate according to a third exemplary embodimentof the present invention;

FIG. 5 is a schematic view showing a state in a process of manufacturinga flexible display substrate according to a fourth exemplary embodimentof the present invention;

FIG. 6 is a schematic structural view of the flexible display substrateaccording to the first exemplary embodiment of the present invention;

FIG. 7 is a schematic structural view of the flexible display substrateaccording to the second exemplary embodiment of the present invention;

FIG. 8 is a schematic structural view of the flexible display substrateaccording to the third exemplary embodiment of the present invention;

FIG. 9 is a schematic structural view of the flexible display substrateaccording to the fourth exemplary embodiment of the present invention;

FIG. 10 is a schematic view showing a state in a process ofmanufacturing a flexible display substrate according to a fifthexemplary embodiment of the present invention;

FIG. 11 is a schematic view showing a state in a process ofmanufacturing a flexible display substrate according to a sixthexemplary embodiment of the present invention;

FIG. 12 is a schematic structural view of the flexible display substrateaccording to the fifth exemplary embodiment of the present invention;and

FIG. 13 is a schematic structural view of the flexible display substrateaccording to the sixth exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

In order to clearly and completely understand the technical solution ofthe present invention, exemplary embodiments of the present disclosurewill be described hereinafter in detail with reference to the attacheddrawings. Obviously, the described embodiments are merely part of theembodiments of the present invention, rather than all of the embodimentsof the present invention. Based on the embodiments of the presentinvention, other embodiments acquired by the person skilled in the artwithout any inventive effort will be within the protection scope of thepresent invention.

According to the general inventive concept of the present invention,there is provided a flexible display substrate comprising a flexiblebase, a first buffer layer and a second buffer layer disposed on anupper surface and a lower surface of the flexible base, respectively,and a plurality of display modules disposed on the first buffer layer,each of display modules includes at least one thin film transistor andat least one electrode corresponding to the thin film transistor.

A method for manufacturing a flexible display substrate according toexemplary embodiments of the present invention comprises steps of:providing a support substrate, forming a second buffer layer on thesupport substrate, disposing a flexible base on the second buffer layer,forming a first buffer layer on the flexible base, forming a pluralityof display modules on the first buffer layer, each of the plurality ofdisplay modules including at least one thin film transistor and at leastone electrode corresponding to the thin film transistor, and separatingthe support substrate from the second buffer layer so as to form theflexible display substrate.

In general, the thin film transistor includes a gate electrode, a gateinsulating layer, an active layer, a source electrode and a drainelectrode. In this case, the flexible display substrate furthercomprises a gate line electrically connected with the gate electrode, agate line lead, a data line electrically connected with the sourceelectrode and a data line lead.

It is noted that, firstly, in various embodiments of the presentinvention, each of the display modules may be understood to be astructure necessary for realizing a display function which is disposedon the flexible base and is formed by respective pattern layers.

Secondly, the at least one electrode may be different according todifferent types of the flexible display substrate. For example, when theflexible display substrate is used as an array substrate of a liquidcrystal display (LCD), the at least one electrode includes a pixelelectrode, and may also include a common electrode. In this case, eachof display modules may include the thin film transistor and the pixelelectrode electrically connected with the drain electrode of the thinfilm transistor, and may also include the common electrode and aninterlayer insulating layer. When the flexible display substrate is usedas an organic light-emitting diode (OLED) display substrate, the atleast one electrode includes an anode and a cathode. In this case, eachof the display modules may the thin film transistor, the anodeelectrically connected with the drain electrode of the thin filmtransistor and the cathode, and may also include an organic materialfunctional layer interposed between the anode and the cathode. Here, dueto particularity of a material of the organic material functional layer,it is necessary to form a packaging layer for packaging the organicmaterial after forming the display modules as described above.

Thirdly, the thin film transistor is a semiconductor unit havingswitching characteristic. For example, the thin film transistor may bean amorphous silicon thin film transistor, or a low temperaturepolycrystalline silicon thin film transistor, or an oxide thin filmtransistor, or an organic thin film transistor and the like, and is notlimited herein.

The thin film transistor may be a top-gate type or a bottom-gate typethin film transistor, and is not limited herein. The top-gate type andthe bottom-gate type thin film transistors are defined based onpositions of the gate electrode and the gate insulating layer,respectively. That is, with respect to the flexible base, when the gateelectrode is disposed close to the flexible base and the gate insulatinglayer is disposed away from the flexible base, the thin film transistormay be referred to the bottom-gate type thin film transistor; when thegate electrode is disposed away from the flexible base and the gateinsulating layer is disposed close the flexible base, the thin filmtransistor may be referred to the top-gate type thin film transistor.

Fourthly, in various embodiments of the present invention, the terms“above” and “below” are defined based on a manufacturing processsequence. In the process for manufacturing the flexible displaysubstrate, components prior formed are located below, and componentslater formed are located above.

For example, the first buffer layer is located above the flexible base,and the second buffer layer is located below the flexible base. That is,the second buffer layer is prior formed, and then the flexible base, andfinally the first buffer layer is formed, on the support substrate.

Fifthly, in various embodiments of the present invention, both the firstbuffer layer and the second buffer layer preferably are selected fromsuch film layers that are not patterned unless otherwise statement.

In the method for manufacturing the flexible display substrate accordingto embodiments of the present invention, on one hand, it is possible tocause strong adhesion forces to be generated between the first bufferlayer and the flexible base as well as between the first buffer layerand the film layer located above the first buffer layer by forming thefirst buffer layer on the upper surface of the flexible base, therebynot only solving a problem that the surface of the flexible base isrough, but also avoiding break and peeling of the film layer disposed onthe flexible base; on the other hand, it is possible to counteract apart of stresses applied to the flexible base by the film layer locatedabove the flexible base by forming the second buffer layer between thesupport substrate and the flexible base 102, so that the degree of thewarpage occurred in the flexible base when separating the supportsubstrate 101 from the flexible base 102 is reduced.

According to an exemplary embodiment of the present invention, a methodfor manufacturing a flexible substrate comprises:

S01: forming a second buffer layer 202 on a support substrate 101, asshown in FIG. 1. The support substrate 101 may be a glass substrate. Thesecond buffer layer 202 may have a single-layer or multilayer structure.A material for forming the second buffer layer 202 may be at least oneof silicon nitride (SiN), silicon oxide (SiOx), Amorphous Silicon(A-Si), and Indium Tin Oxide (ITO).

S02: forming a flexible base 102 on the second buffer layer 202, asillustrated in FIG. 1. A material for forming the flexible base 102 maybe at least one of polyimide, polycarbonate, polyacrylate,polyetherimide, polyethersulfone, Polyethylene terephthalate, andpolyethylene naphthalate.

S03: forming a first buffer layer 201 on the flexible base 102, as shownin FIG. 1. A material for forming the first buffer layer 201 may be thesame as that of the second buffer layer 202.

S04: forming a plurality of display modules on the first buffer layer201, each of the plurality of display modules including at least onethin film transistor 30 and at least one electrode corresponding to thethin film transistor 30.

It will be appreciated for those skilled in the art that pattern layerssuch as a protection layer and a passivation layer necessary forrealizing corresponding functions of the flexible display substrate maybe further formed according to different types of the flexible displaysubstrate expect for forming the at least one thin film transistor 30and the at least one electrode.

A flexible display substrate and a method for manufacturing the sameaccording to various exemplary embodiments of the present invention willbe described below with reference to accompany drawings.

FIG. 2 is a schematic view showing a state in a process formanufacturing a flexible display substrate according to a firstexemplary embodiment of the present invention. As shown in FIG. 2, theat least one electrode includes a pixel electrode 401 which iselectrically connected with a drain electrode 305 of the thin filmtransistor 30 through a via hole formed in a protection layer formedtherebetween.

FIG. 3 is a schematic view showing a state in a process formanufacturing a flexible display substrate according to a secondexemplary embodiment of the present invention. The flexible displaysubstrate according to the second exemplary embodiment as shown in FIG.3 is obtained by further forming common electrodes 402 on the basis ofthe flexible display substrate according to the first exemplaryembodiment as shown in FIG. 2. In this case, in the step S04, a gatemetal layer including a gate electrode 301 and a gate line (not shown),a gate insulating layer 302, a semiconductor active layer 303, asource-drain metal layer including a source electrode 304, a drainelectrode 305 and a data line (not shown), the pixel electrode 401 andthe common electrodes 402 are sequentially formed on the first bufferlayer 201. In the embodiment as shown in FIG. 3, the pixel electrode 401and the common electrodes 402 are respectively formed on differentlayers with a passivation layer being formed therebetween.

FIG. 4 is a schematic view showing a state in a process formanufacturing a flexible display substrate according to a thirdexemplary embodiment of the present invention. The difference betweenthe flexible display substrates as shown in FIG. 4 and that shown inFIG. 3 is in that the pixel electrode 401 is formed on the same layer asthe common electrodes 402.

FIG. 5 is a schematic view showing a state in a process formanufacturing a flexible display substrate according to a fourthexemplary embodiment of the present invention. The flexible displaysubstrate according to the fourth exemplary embodiment as shown in FIG.5 is a modification to that according to the first exemplary embodimentas shown in FIG. 2. As shown in FIG. 5, in the flexible displaysubstrate according to the fourth exemplary embodiment, the at least oneelectrode further includes an anode 403 and a cathode 404. In this case,in the step S04, a gate metal layer including a gate electrode 301 and agate line (not shown), a gate insulating layer 302, a semiconductoractive layer 303, a source-drain metal layer including a sourceelectrode 304, a drain electrode 305 and a data line (not shown), theanode 401, an organic material functional layer 501, the cathode 402 anda packaging layer 60 are sequentially formed on the first buffer layer201. The anode 403 is electrically with the drain electrode 305 througha via hole in a protection layer formed therebetwwen.

The organic material functional layer 501 at least includes an electrontransporting layer, a light-emitting layer and a hole transportinglayer. In order to improve the efficiency of injecting electrons andholes into the light-emitting layer, the organic material functionallayer may further include an electron injecting layer disposed betweenthe cathode and the electron transporting layer and a hole injectinglayer disposed between the anode and the hole transporting layer.

The method for manufacturing the flexible display substrate according tothe exemplary embodiment of the present invention further comprises astep S05 of separating the support substrate 101 from a film layer incontact with the support substrate 101 to form various flexible displaysubstrates as shown in FIGS. 6 through 9 after forming the displaymodules.

According to an exemplary embodiment of the present invention, thesupport substrate 101 is separated from the second buffer layer 202 indirect contact with support substrate 101 in a manner of laserradiation.

Further, both the first buffer layer 201 and the second buffer layer 202include a single buffer film layer or a plurality of buffer film layers.That is, any one of the first buffer layer 201 and the second bufferlayer 202 includes at least one buffer film layer.

In a case where both the first buffer layer 201 and the second bufferlayer 202 include the plurality of buffer film layers, all the bufferfilm layers of the first buffer layer 201 and the second buffer layer202 are symmetrically formed with respect to the flexible base 102.

For example, if the first buffer layer 201 includes a silicon oxidelayer and a silicon nitride layer and the second buffer layer 202includes a silicon oxide layer and a silicon nitride layer, then thefirst buffer layer 201 and the second buffer layer 202 are symmetricallydisposed with respect to the flexible base 102. Specifically, thesilicon oxide layer and the silicon nitride layer are firstlysequentially formed on the support substrate 101, and then the flexiblebase 102 is formed, thereafter, the silicon oxide layer and the siliconnitride layer are sequentially formed on the flexible base 102, whereinthe two processes of forming the silicon oxide layer and the siliconnitride layer are completely the same as each other.

In this way, when the first buffer layer 201 and the second buffer layer202 are symmetrically disposed with respect to the flexible base 102, itis possible to maximumly counteract stresses applied to the flexiblebase 102 by the first buffer layer 201 and the second buffer layer 202and to reduce degree of a warpage occurred in the flexible base 102 whenseparating the support substrate 101 from the flexible base 102.

Further, it is possible to form the first buffer layer 201 and thesecond buffer layer 202 by the same process condition.

Here, a thickness of each of the first buffer layer 201 and the secondbuffer layer 202 is set, for example, between 1000 and 5000 Å.

Since the first buffer layer 201 and the second buffer layer 202 locatedabove and below the flexible base 102 respectively are made of the samematerial, have the same thickness and structure, and the first bufferlayer 201 and the second buffer layer 202 are symmetrically disposedwith respect to the flexible base 102, it is possible to completelycounteract the stresses applied to the flexible base 102 by the firstbuffer layer 201 and the second buffer layer 202.

Based on the above discussion, the method for manufacturing the flexibledisplay substrate according the exemplary embodiments of the presentinvention further comprises a step of forming a plurality of auxiliaryfilm layers between the second buffer layer 202 and the supportsubstrate 101. Each of the plurality of auxiliary film layers is made ofthe same material and has the same thickness as each pattern layer ofthe thin film transistor 30. In a case of forming the plurality ofauxiliary film layers, the support substrate 101 is separated from oneof the plurality of auxiliary film layers which is in contact with thesupport substrate 101 in the step of separating the support substrate101 from the second buffer layer 202. In this way, the plurality ofauxiliary film layers are still remained on the second buffer layer 202after separating, as shown in FIG. 12.

In this way, it is possible to counteract most of the stresses appliedto the flexible base 102 by all the film layers located above theflexible base 102 by a combined action of the second buffer layer 202and the plurality of auxiliary film layers located therebelow, therebyfurther reducing the degree of the warpage occurred in the flexible base102 when separating the support substrate 101 from the flexible base102.

Further, for the flexible base 102, it is possible to allow an order offorming the plurality of auxiliary film layers between the second bufferlayer 202 and the support substrate 101 to be the same as that ofarranging the respective pattern layer of the thin film transistor whichare made of the same materials as the auxiliary film layers.

FIG. 10 is a schematic view showing a state in a process formanufacturing a flexible display substrate according to a fifthexemplary embodiment of the present invention. The flexible displaysubstrate according to the fifth exemplary embodiment as shown in FIG.10 is a modification to that according to the fourth exemplaryembodiment as shown in FIG. 5. As illustrated in FIG. 10, in a casewhere the patterns of the thin film transistor 30 sequentially include agate metal layer, a gate insulating layer, a semiconductor active layer,and a source-drain metal layer, a plurality of auxiliary film layers arecorrespondingly formed between the second buffer layer 202 and thesupport substrate 101. The auxiliary film layers include a first filmlayer 701 made of the same material and having the same thickness as thegate metal layer, a second film layer 702 made of the same material andhaving the same thickness as the gate insulating layer, a third filmlayer 703 made of the same material and having the same thickness as thesemiconductor active layer, and a fourth film layer 704 made of the samematerial and having the same thickness as the source-drain metal layer.That is, the fourth film layer 704, the third film layer 703, the secondfilm layer 702, the first film layer 701 and the second buffer layer 202are firstly sequentially formed on the support substrate 101,thereafter, the flexible base 102 is formed on the second buffer layer202, and then the first buffer layer 201 is formed on the flexible base102, and the gate metal layer, the gate insulating layer, thesemiconductor active layer and the source-drain metal layer aresequentially formed on the first buffer layer 201.

Since the plurality of auxiliary film layers and the respective patterlayers of the thin film transistor 30 are made of the same material andhave the same thickness, and the arranging orders thereof with respectto the flexible base 102 are the same as each other i.e., the pluralityof auxiliary film layers are symmetrically disposed with the respectivepattern layers of the thin film transistor 30 with respect to theflexible base 102, it is possible to maximumly counteract the stressesapplied to the flexible base 102 by all the film layers including thefirst buffer layer 201 and the thin film transistor 30 which aredisposed above the flexible base 102 by the combined action of thesecond buffer layer 202 and the plurality of auxiliary film layerslocated therebelow.

FIG. 11 is a schematic view showing a state in a process formanufacturing a flexible display substrate according to a sixthexemplary embodiment of the present invention. The flexible displaysubstrate according to the sixth exemplary embodiment as shown in FIG.11 is a modification to that according to the fourth exemplaryembodiment as shown in FIG. 5. The flexible display substrate as shownin FIG. 11 further comprise an auxiliary thin film transistor 30′. In anexemplary embodiment, as illustrated in FIG. 11, based on the method formanufacturing the flexible display substrate as shown in FIG. 5, themethod further comprises a step of forming the auxiliary thin filmtransistor 30′ between the second buffer layer 202 and the supportsubstrate 101, the thin film transistors 30 formed above the firstbuffer layer 201 corresponding to the auxiliary thin film transistors30′ formed below the second buffer layer 202 one by one, respectively.In a case of forming a plurality of auxiliary thin film transistors 30′,in the step of separating the support substrate 101 and the secondbuffer layer 202, the support substrate 101 is separated from a filmlayer of the plurality of auxiliary thin film transistors 30′ which isin contact with the support substrate 101. In this way, afterseparating, the plurality of auxiliary thin film transistors 30′ arestill remained on the second buffer layer 202, as shown in FIG. 13.

Here, the expression “the thin film transistors 30 formed above thefirst buffer layer 201 corresponding to the auxiliary thin filmtransistors 30′ formed below the second buffer layer 202 one by one,respectively” means any one of the thin film transistors 30 locatedabove the first buffer layer 201 always corresponds to one of theauxiliary thin film transistors 30′ located below the second bufferlayer 201 in a vertical direction, and the film layers of the thin filmtransistors 30 formed above the first buffer layer 201 corresponds tothe film layers of the auxiliary thin film transistors 30′ formed belowthe second buffer layer 202 one by one, respectively.

In this way, it is possible to counteract the stresses applied to theflexible base 102 by the first buffer layer 201 and the thin filmtransistors 30 above the flexible base 102 by the combined action of thesecond buffer layer 202 and the auxiliary thin film transistors 30′located therebelow, thereby further reducing the degree of the warpageoccurred in the flexible base 102 when separating the support substrate101 from the flexible base 102.

It is noted that an auxiliary electrode film layer and an auxiliarydisplay film layer may be further formed between the second buffer layer202 and the support substrate 101 according to further exemplaryembodiments of the present invention. The auxiliary electrode film layeris made of the same material and has the same thickness as the at leastone electrode. The auxiliary display film layer is made of the samematerial and has the same thickness as other film layers necessary forthe display modular.

According to further exemplary embodiments of the present invention,there is further provided a flexible display substrate 10. Asillustrated in FIGS. 6 through 9, the flexible display substrate 10comprises a flexible base 102, a first buffer layer 201 and a secondbuffer layer 202 disposed on an upper surface and a lower surface of theflexible base 102 respectively, and a plurality of display modulesdisposed on the first buffer layer 201, each of which includes at leastone thin film transistor 30 and at least one electrode corresponding tothe thin film transistor 30.

The thin film transistor 30 includes a gate electrode 301, a gateinsulating layer 302, an active layer 303, a source electrode 304 and adrain electrode 305. In this case, the flexible display substrate 10further comprises a gate line electrically connected with the gateelectrode 301, a gate line lead, a data line electrically connected withthe source electrode 304, and a data line lead.

When the flexible display substrate 10 is used as an array substrate ofa liquid crystal display, the at least one electrode may include a pixelelectrode 401 connected with the drain electrode 305, as shown in FIG.6. The at least one electrode may further include a common electrode402, as illustrated in FIGS. 7 and 8. In this case, for an In-PlaneSwitch (IPS) array substrate, as shown in FIG. 8, the pixel electrode401 is disposed in the same layer as the common electrode 402 and spacedapart therefrom, and both the pixel electrode 401 and the commonelectrode 402 are provided as strip electrodes. For an Advanced-superDimensional Switching (ADS) array substrate, as show in FIG. 7, thepixel electrode 401 is disposed in a different layer from the commonelectrode 402, and one of the pixel electrode 401 and the commonelectrode 402 located above is provided as a strip electrode, and theother of the pixel electrode 401 and the common electrode 402 locatedbelow is provided as a plate electrode.

When the flexible display substrate 10 is used as an organiclight-emitting diode display substrate, the at least one electrode mayinclude an anode 403 connected with the drain electrode 305 and acathode 404, as shown in FIG. 9. In this case, each of the displaymodules further includes an organic material functional layer 501interposed between the anode 403 and the cathode 404. Further, theflexible display substrate 10 further comprises a packaging layer 60.

Based on this, the flexible display substrate 10 may be divided into asingle-side light emitting type flexible display substrate and adouble-side light emitting type flexible substrate according todifference between the materials for forming the anode 403 and thecathode 404. That is, when the material for forming one of the anode 403and the cathode 404 is an opaque material, the flexible displaysubstrate is the single-side light emitting type flexible displaysubstrate. When both the materials for forming the anode 403 and thecathode 404 are transparent materials, the flexible display substrate isthe double-side light emitting type flexible display substrate.

The single-side light emitting flexible display substrate may be furtherdivided into a top light emitting type flexible display substrate and abottom light emitting type flexible display substrate according to thedifference between the materials for forming the anode 403 and thecathode 404. Specifically, when the anode 403 is disposed close to theflexible base 102, the cathode 404 is disposed away from the flexiblebase 102, the material for forming the anode 403 is a transparentconductive material, if the material for forming the cathode 404 is anopaque conductive material, since a light is emitted out through oneside of the flexible base 102 from the anode 403, the flexible displaysubstrate may be referred as the bottom light emitting type flexibledisplay substrate; if the material for forming the anode 403 is theopaque conductive material, and the material for forming the cathode 404is the transparent conductive material, since the light is emitted outthrough the packaging layer 60 opposed to the flexible base 102 from thecathode 404, the flexible display substrate may be referred as the toplight emitting type flexible display substrate. Of course, a relativeposition of the anode 403 and the cathode 404 may be reversed, and thedescription thereof in details is omitted herein.

Here, the packaging layer 60 may be a flexible packaging substrate, ormay have one or more thin film layers. However, the packaging layer 60may also have other packaging structures, and is not limited to herein.

For the double-side light emitting type flexible display substrate, whenthe anode 403 is disposed close to the flexible base 102, the cathode404 is disposed away from the flexible base 102, both the materials forforming the anode 403 and the cathode 404 are transparent conductivematerials such as Indium Tin Oxide (ITO), since the light, on one hand,is emitted out through one side of the flexible base 102 from the anode403, and, on the other hand, is emitted out through the packaging layeropposed to the flexible base 102 from the cathode 404, the flexibledisplay substrate may be referred as the double-side light emitting typeflexible display substrate. Here, it is also possible to provide theanode 403 away from the flexible base 102 and to provide the cathode 404close to the flexible base 102.

Based on the above discussion, each of the display modules may alsocomprise pattern layers necessary for realizing a display function, suchas a protection layer, a passivation layer, an interlayer insulatinglayer, a pixel isolating layer for isolating pixel units, or additionalpattern layers for improving the display effect or for overcoming somedefects. However, when the flexible display substrate 10 is the OLED,each of the display modules should also comprise the organic materialfunctional layer 501 located between the anode 403 and the cathode 404,and the packaging layer 60 for packaging the organic material functionallayer 501.

Embodiments of the present invention provide a flexible displaysubstrate 10 comprising a flexible base 102, a first buffer layer 201and a second buffer layer 202 disposed on an upper surface and a lowersurface of the flexible base 102, respectively, and a plurality ofdisplay modules disposed on the first buffer layer 201, each of whichincludes at least one thin film transistor 30 and at least one electrodecorresponding to the thin film transistor 30.

On one hand, it is possible to cause strong adhesion forces to begenerated between the first buffer layer 201 and the flexible base 102as well as between the first buffer layer 201 and the film layer locatedabove the first buffer layer 201 by forming the first buffer layer 201on the upper surface of the flexible base 102, thereby not only solvinga problem that the surface of the flexible base 102 is rough, but alsoavoiding break and peeling of the film layer provided on the flexiblebase 102.

On the other hand, it is possible to counteract a part of stressesapplied to the flexible base 102 by the film layer located above theflexible base 102 by forming the second buffer layer 202 between thesupport substrate 101 and the flexible base 102, so that the degree ofthe warpage occurred in the flexible base 102 when separating thesupport substrate 101 from the flexible base 102 is reduced.

Preferably, the first buffer layer 201 is made of the same material andhas the same thickness as the second buffer layer 202.

Since the first buffer layer 201 and the second buffer layer 202 locatedabove and below the flexible base 102, respectively, are made of thesame material and have the same thickness and structure, it is possibleto maximumly counteract stresses applied to the flexible base 102 by thefirst buffer layer 201 and the second buffer layer 202 and to reduce thedegree of the warpage occurred in the flexible base 102 when separatingthe support substrate 101 from the flexible base 102.

Further, both the first buffer layer 201 and the second buffer layer 202include a single film layer or a plurality of film layers. In a casewhere both the first buffer layer 201 and the second buffer layer 202include the plurality of film layers, all the film layer of the firstbuffer layer 201 and the second buffer layer 202 are symmetricallydisposed with respect to the flexible base 102.

For example, if the first buffer layer 201 includes a silicon oxidelayer and a silicon nitride layer and the second buffer layer 202includes a silicon oxide layer and a silicon nitride layer, then thefirst buffer layer 201 and the second buffer layer 202 are symmetricallydisposed with respect to the flexible base 102. That is, the siliconoxide layer of the first buffer layer 201 and the silicon oxide layer ofthe second buffer layer 202 are both disposed close to the flexible base102, and the silicon nitride layer of the first buffer layer 201 and thesilicon nitride layer of the second buffer layer 202 are both disposedaway from the flexible base 102.

In this way, when the first buffer layer 201 and the second buffer layer202 are completely symmetrically disposed with respect to the flexiblebase 102, it is possible to completely counteract the stresses appliedto the flexible base 102 by the first buffer layer 201 and the secondbuffer layer 202.

Further, considering an entire thickness of the flexile displaysubstrate 10, in embodiments of the present invention, the thickness ofeach of the first buffer layer 201 and the second buffer layer 202 maybe between 1000 and 5000 Å.

Based on the above discussion, preferably, a plurality of auxiliary filmlayers are further disposed on one side of the second buffer layer 202away from the flexible substrate 102. Each of the auxiliary film layersis made of the same material and has the same thickness as each patternlayer made of the thin film transistor 30.

In this way, it is possible to counteract most of the stresses appliedto the flexible base 102 by all the film layers located above theflexible base 102 by a combined action of the second buffer layer 202and the plurality of auxiliary film layers located below the secondbuffer layer 202, thereby further reducing the degree of the warpageoccurred in the flexible base 102 when separating the support substrate101 from the flexible base 102.

Further preferably, an arranging order of the plurality of auxiliaryfilm layers is same as that of the respective pattern layers of the thinfilm transistor 30 with respect to the flexible base 102.

For example, as shown in FIG. 12, in a case where the pattern layers forforming the thin film transistor 30 sequentially include a gate metallayer, a gate insulating layer, a semiconductor active layer, asource-drain metal layer, the plurality of auxiliary film layers formedon the one side of the second buffer layer 202 away from the flexiblesubstrate 102 include a first film layer 701 made of the same materialand having the same thickness as the gate metal layer, a second filmlayer 702 made of the same material and having the same thickness as thegate insulating layer, a third film layer 703 made of the same materialand having the same thickness as the semiconductor active layer, and afourth film layer 704 made of the same material and having the samethickness as the source-drain metal layer. That is, with respect to theflexible base 102, the gate metal layer, the gate insulating layer, thesemiconductor layer and the source-drain metal layer located above theflexible base 102 are sequentially disposed away from the flexible base102, and the first film layer 701, the second film layer 702, the thirdfilm layer 703 and the fourth film layer 704 located below the flexiblebase 102 are sequentially disposed away from the flexible base 102

Since the thin film transistors 30 and the plurality of auxiliary filmlayers are made of the same material and have the same thickness, andthe arranging orders thereof with respect to the flexible base 102 arethe same as each other, i.e., it may be understood that the thin filmtransistors 30 and the plurality of auxiliary film layers aresymmetrically disposed with respect to the flexible base 102, it ispossible to maximumly counteract the stresses applied to the flexiblebase 102 by all the film layers including the first buffer layer 201 andthe thin film transistors 30 which are disposed above the flexible base102, by the combined action of the second buffer layer 202 and theplurality of auxiliary film layers located therebelow.

Alternatively, as illustrated in FIG. 13, the auxiliary thin filmtransistors 30′ are further disposed on one side of the second bufferlayer 202 which are away from the flexible base 102, and the thin filmtransistors 30 formed above the first buffer layer 201 corresponds tothe auxiliary thin film transistors 30′ formed below the second bufferlayer 202 one by one, respectively.

It should be noted that the expression “the thin film transistors 30formed above the first buffer layer 201 corresponds to the auxiliarythin film transistors 30′ formed below the second buffer layer 202 oneby one, respectively” means any one of the thin film transistors 30located above the first buffer layer 201 always corresponds to one ofthe auxiliary thin film transistors 30′ located below the second bufferlayer 201 in a vertical direction, and the film layers of the thin filmtransistors 30 located above the first buffer layer 201 corresponds tothe film layers of the auxiliary thin film transistors 30′ located belowthe second buffer layer 202 one by one, respectively.

In this way, it is possible to counteract the stresses applied to theflexible base 102 by the first buffer layer 201 and thin filmtransistors 30 above the flexible base 102 by the combined action of thesecond buffer layer 202 and the auxiliary thin film transistors 30′located therebelow, thereby further reducing the degree of the warpageoccurred in the flexible base 102 when separating the support substrate101 and the flexible base 102.

It is noted that an auxiliary electrode film layer and an auxiliarydisplay film layer may be further formed between the second buffer layer202 and the support substrate 101 according to further exemplaryembodiments of the present invention. The auxiliary electrode film layeris made of the same material and has the same thickness as the at leastone electrode. The auxiliary display film layer is made of the samematerial and has the same thickness as other film layers necessary forthe display modular.

Moreover, it should be appreciated for those skilled in the art that abottom-gate type thin film transistor is illustrated as an example inall the accompany drawings of the embodiments of the present invention.The present invention, however, is not limited to herein, and the thinfilm transistor may any type thin film transistor.

Although several exemplary embodiments have been shown and describedabove, the present invention is not limited herein, and it would beappreciated by those skilled in the art that various changes ormodifications may be made in these embodiments without departing fromthe principle and spirit of the disclosure, the scope of which isdefined in the claims and their equivalents.

1. A flexible display substrate comprising: a flexible base; a firstbuffer layer and a second buffer layer disposed on an upper surface anda lower surface of the flexible base, respectively; and a plurality ofdisplay modules disposed on the first buffer layer, each display moduleincluding at least one thin film transistor and at least one electrodecorresponding to the thin film transistor.
 2. The flexible displaysubstrate according to claim 1, wherein the first buffer layer and thesecond buffer layer are made of the same material and have the samethickness.
 3. The flexible display substrate according to claim 2,wherein any one of the first buffer layer and the second buffer layerincludes at least one buffer film layer; and all the buffer film layersof the first buffer layer and all the buffer film layers of the secondbuffer layer are symmetrically disposed with respect to the flexiblebase, respectively.
 4. The flexible display substrate according to claim2, wherein a thickness of each of the first buffer layer and the secondbuffer layer is set between 1000 and 5000 Å.
 5. The flexible displaysubstrate according to claim 1, wherein a plurality of auxiliary filmlayers are disposed on one side of the second buffer layer which is awayfrom the flexible base, each of the auxiliary film layers being made ofthe same material and having the same thickness as each pattern layer ofthe thin film transistor.
 6. The flexible display substrate according toclaim 5, wherein an arranging order of the plurality of auxiliary filmlayers is same as that of the respective pattern layers of the thin filmtransistor with respect to the flexible base.
 7. The flexible displaysubstrate according to claim 1, wherein a plurality of auxiliary thinfilm transistors are disposed on one side of the second buffer layerwhich is away from the flexible base, the auxiliary thin filmtransistors corresponding to the thin film transistors one by one,respectively.
 8. The flexible display substrate according to claim 1,wherein the at least one electrode includes a cathode, and an anodeelectrically connected with a drain electrode of the thin filmtransistor; and each of the display modules further includes a packaginglayer, and an organic material functional layer disposed between thecathode and the anode.
 9. The flexible display substrate according toclaim 1, wherein the at least one electrode include a pixel electrodeelectrically connected with a drain electrode of the thin filmtransistor.
 10. A method for manufacturing a flexible display substratecomprising steps of: forming a second buffer layer on a supportsubstrate; providing a flexible base on the second buffer layer; forminga first buffer layer on the flexible base; forming a plurality ofdisplay modules on the first buffer layer, each of the plurality ofdisplay modules including at least one thin film transistor and at leastone electrode corresponding to the thin film transistor; and separatingthe support substrate from the second buffer layer.
 11. The methodaccording to claim 10, wherein the first buffer layer and the secondbuffer layer are formed under the same process condition.
 12. The methodaccording to claim 10, wherein any one of the first buffer layer and thesecond buffer layer includes at least one buffer film layer; and all thebuffer film layers of the first buffer layer and all the buffer filmlayers of the second buffer layer are symmetrically disposed withrespect to the flexible base, respectively.
 13. The method according toclaim 10, further comprising steps of: forming a plurality of auxiliaryfilm layers between the second buffer layer and the support substrate,the auxiliary film layers being made of the same materials and havingthe same thicknesses as pattern layers of the thin film transistor,respectively; and separating the support substrate from one of theplurality of auxiliary film layers which is in contact with the supportsubstrate in the step of separating the support substrate from thesecond buffer layer.
 14. The method according to claim 13, wherein anarranging order of the plurality of auxiliary film layers is same asthat of the respective pattern layers of the thin film transistor withrespect to the flexible base.
 15. The method according to claim 10,further comprising steps of: forming a plurality of auxiliary thin filmtransistors between the second buffer layer and the support substrate,the auxiliary thin film transistors corresponding to the thin filmtransistors one by one, respectively; and separating the supportsubstrate from one of the plurality of auxiliary thin film transistorswhich is in contact with the support substrate in the step of separatingthe support substrate from the second buffer layer.
 16. The flexibledisplay substrate according to claim 3, wherein a plurality of auxiliaryfilm layers are disposed on one side of the second buffer layer which isaway from the flexible base, each of the auxiliary film layers beingmade of the same material and having the same thickness as each patternlayer of the thin film transistor.
 17. The flexible display substrateaccording to claim 16, wherein an arranging order of the plurality ofauxiliary film layers is the same as that of the respective patternlayers of the thin film transistor with respect to the flexible base.18. The flexible display substrate according to claim 3, wherein aplurality of auxiliary thin film transistors are disposed on one side ofthe second buffer layer which is away from the flexible base, theauxiliary thin film transistors corresponding to the thin filmtransistors one by one, respectively.
 19. The method according to claim12, further comprising steps of: forming a plurality of auxiliary filmlayers between the second buffer layer and the support substrate, theauxiliary film layers being made of the same materials and having thesame thicknesses as pattern layers of the thin film transistor,respectively; and separating the support substrate from one of theplurality of auxiliary film layers which is in contact with the supportsubstrate in the step of separating the support substrate from thesecond buffer layer.
 20. The method according to claim 12, furthercomprising steps of: forming a plurality of auxiliary thin filmtransistors between the second buffer layer and the support substrate,the auxiliary thin film transistors corresponding to the thin filmtransistors one by one, respectively; and separating the supportsubstrate from one of the plurality of auxiliary thin film transistorswhich is in contact with the support substrate in the step of separatingthe support substrate from the second buffer layer.